Comparison of histochemical properties of different pig breeds.

The study involved 158 pigs: 51 Hampshire (H), 54 Landrace (L) and 53 Yorkshire (Y). The aim of the study was to compare muscle histochemical properties of M. longissimus dorsi and adductor between muscles from pigs of purebred Hampshire, Landrace and Yorkshire lineages. The following histochemical properties were determined: 1) the percentage of type I, IIA and IIB fibers in number (calculated on the basis of the number of different fiber types) and area (calculated on the basis of the area of different fiber types) as analyzed with the myosin ATPase method using an acid preincubation solution of pH 4.6; 2) the cross sectional area of each fiber type; 3) the percentage of oxidative fibers on the basis of the NADH-TR method; and 4) the capillary density of the muscles. The cross-sectional area of type IIB fibers was the largest in Landrace. The highest capillary density (capillaries per mm(2)), 254 ± 38, was in longissimus of Hampshire. A positive correlation between M. longissimus dorsi and M. adductor was found in the percentage of type I, IIA and IIB fibers in number and area, cross-sectional area of each fiber type, and capillary density. The differences in histochemical properties between breeds were, however, smaller in M. adductor than in longissimus dorsi muscle. In addition, the variation in muscle fiber composition in pigs within the breeds was larger than the average variation between the breeds.